1. Field
The present disclosure relates to a non-precious metal based water electrolysis catalyst for both oxygen evolution at an anode and hydrogen evolution at a cathode and a method for preparing the same. More particularly, the present disclosure relates to a non-precious metal based water electrolysis catalyst based on a cobalt-containing compound fixed to a carbon carrier and a method for preparing the same.
[Description about National Support Research and Development]
This study is made by the support of core research business of Korea Ministry of Science, ICT and Future Planning under the supervision of Korea Institute of Science and Technology, and the subject name thereof is Development of Fundamental Source Technology for Preparation of High-Quality Membrane-Electrode Assembly for Polymer Electrolyte Fuel Cells Using Non-Platinum Based Catalyst (Subject Identification No.:2014003865).
2. Description of the Related Art
As energy demand has increased, active studies have been made about economical and eco-friendly substitute energy conversion and storage systems. Particularly, conversion of water into oxygen and hydrogen corresponds to core energy conversion technology and belongs to regenerated resource storage technology in the form of chemical fuel. Recently, electrochemical hydrogen production largely depends on general water electrolysis processes and chloro-alkali industry. In fact, decomposition of water is regarded as a method for supplying hydrogen in an eco-friendly, economical and sustainable manner. Therefore, development of more effective and stable catalyst electrode materials has been regarded significantly. Water electrolysis may be broadly divided into two types of half cell reactions, one of which is hydrogen evolution reaction (HER) occurring at a cathode and the other of which is oxygen evolution reaction (OER) occurring at an anode. In terms of practical applicability, oxygen evolution reaction has a more complicated mechanism and requires a larger overvoltage as compared to hydrogen evolution reaction, and thus development of an efficient and stable catalyst for oxygen evolution reaction is very important to accomplish commercialization of large-scale hydrogen production based on water electrolysis. Although precious metal oxide catalysts such as RuO2 and IrO2 show high activity, they are not amenable to large-scale application due to their high cost and scarcity. Therefore, there has been a need for technology of developing an efficiency catalyst capable of substituting for high-cost catalysts from materials abundant in the earth. Particularly, since oxygen evolution reaction under acidic atmosphere severely limits the use of a non-precious metal based catalyst, there have been suggested non-precious metal based catalysts for oxygen evolution under alkaline atmosphere. Meanwhile, also in the case of hydrogen evolution reaction, development of non-platinum based catalysts has been conducted actively to substitute for expensive Pt-based catalysts. However, unlike the case of oxygen evolution reaction, there is a problem in that the catalysts function only under acidic atmosphere. When viewed from the point of using non-precious metal based catalysts, such incompatibility is regarded as a big obstacle considering the ultimate completion of water electrolysis based on non-precious metal based catalysts. As a result, there has been an imminent need for developing a non-precious metal based catalyst for hydrogen evolution reaction under alkaline atmosphere.
Referring to oxygen evolution reaction, cobalt has been given many attentions among non-precious metals. There have been designed cobalt oxide-based oxygen evolution reaction (OER) catalysts including Co3O4, Co3O4-based hybrid and substitute cobaltite (MxCo3-xO4) for water oxidation potential.
In addition, more recently, cobalt phosphide (CoP) has been given many attentions by virtue of a low charge-discharge potential and unique magnetic property. However, the electrocatalytic surface property of cobalt phosphide, particularly the property at the oxidation potential and characterization thereof as an oxygen evolution reaction catalyst have been hardly made.